Electric motor control system



J 195] A. J. HORNFECK 2,557,824

ELECTRIC MOTOR CONTROL SYSTEM Filed March 31, 1945 6 Sheets-Sheet 1 FIG.I

FIG. IO

1 I llllllllllllllll 3nvcmor ANTHONY J. HORNFECK June 19, 1951 A. J.HORNFECK ELECTRIC MOTOR CONTROL SYSTEM 6 Sheets-Sheet 2 Filed March 31,1945 Du -@03 5 ZOPOE cmuza dm mm I amora -4m INVENTOR.

ANTHONY J. HORNFECK June 19, 1951 A. J. HORNFECK suzcmc MOTOR comm.SYSTEM 6 Sheets-Sheet 3 Filed March 31, 1945 REVERSING AT VARIABLE SPEEDBRIDGE X BRIDGE INPUT 49 L K R C m m m m V 0 w. J m m P K K K K CE WM NW K AG OB B A m BA H- -A B T D DU 8 0L IIE E D E0 WE EW E m V F F E .E Fv lll u: 1| I-.. 1:: T W U A W n m m w E I F a T m W 1 35 SEW TIMENEu'rRAL FIG. 5

June 19, 1951 A. J. HORNFECK 2,557,824

ELECTRIC MOTOR CONTROL SYSTEM Filed March 31, 1945 6 Sheets-Sheet 4 .I 9NEUTRAL FULL SPEED INTERMEDIATE SPEED ZERO SPEED I E OR E NEUTRAL MOTORcoNomqN IIA LINE I RE, AT OTHER EXTREME ,:E; AT oNE EXTREME I! I! IMOTOR I4A E. 0R LINE NEUTRAL CONDITION -t T T I E A o hER EXTREN [MENTORANTHONY J. HORNFECK ii iifM June 19, 195] A. J. HORNFECK ELECTRIC MOTORCONTROL SYSTEM Filed March 31, 1945 6 Sheets-Sheet 5 IOQAIOfi g) W5 W2FIG. I3

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I09 lO8 O n2 '4 Zhmcntor ANTHONY J. HORNFECK 47* Gttorneg June 19, 1951A. J. HORNFECK 2,557,824

ELECTRIC MOTOR CONTROL SYSTEM Filed March 31, 1945 6 Sheets-Sheet 6 FIG.I7

DC. BIAS INVENTOR.

ANTHONY J. HORNFECK BY WWW FIG. l6

Patented June 19, 1951 ELECTRIC MOTOR CONTROL SYSTEM Anthony J.Hornfeck, Cleveland Heights, Ohio,

assignor to Bailey Meter Company, a corporation of Delaware ApplicationMarch 31, 1945, Serial No. 585,891

18 Claims. (Cl. 318345) This invention relates to measuring andcontrolling systems and apparatus, and more particularly to electricalcircuits for motors and other controlling means used in connection withcontour control or dupllcators for machine tools such as lathes,shapers, planers, milling machines, die sinking machines, and the like.It is, of course, to be understood that my invention is not limited touse with contour control for machine tools, but finds ready applicationin many other embodiments.

An object of my invention is to provide a contour control wherein adesired contour or shape is accurately produced on a work piece,thereafter requiring a minimum of hand finishing.

Still another object of my invention is to pro vide a contour control foa duplicator which may be readily applied to a wide variety of ma chinetools or material working machines.

A further object is to provide improved electrical circuits for motorsand other controlling apparatus sensitive to minute forces or movements.

Further objects will be apparent from the description and drawings inwhich: I

Fig. 1 is a plan view of a lathe embodying a contour control system.

Fig. 2 is an electric circuit diagram of the transverse motor control ofFig. 1.

Fig. 3 is a plot of voltage conditions in tubes A and B of Fig. 2.

Fig. 4 is a plot of voltage conditions through the armature of motor I Iin Fig. 2.

Fig. 5 is a plot of motor speed vs. time for the motor of Fig. 2.

Fig. 6 is an,electric circuit diagram of the longitudinal travel motorof Fig. 2.

Fig. 7 is a' graph in connection with Fig. 6.

Fig. 8 is an electric circuit diagram of simultaneous control of the twomotors of Fig. 1.

Fig. 9 is a graph of conditions in Fig. 8.

Fig. 10 is a plan view of a portion of a vertical milling machine.

Fig. 11 is an elevation of the vertical milling machine of Fig. 10.

Fig. 12 is a plan view of a lathe similar to Fig. 1, but includinganother embodiment of my invention.

Fig. 13 is a diagrammatic showing of the control for the lathe of Fig.12.

Fig. 14 is a switching valve arrangement.

Fig. 15 is a wiring diagram of a measuring circuit.

Fig. 16 shows a modification of a portion of the circuit of Fig. l5.

Fig. 17 is a motor control circuit.

As is well understood by those familiar with the art, in some machinetools, such as lathes, the tool is moved longitudinally and transverselyof the work piece which, except for rotation about its center, remainsstationary. In other machine tools, such as some types of millingmachines, the work piece may be moved in two directions while the tool,except for rotation about its axis, remains stationary. In some othertypes of milling machines and in some die sinking machines the tool maybe moved in one, two or three directions and the work piece may also bemoved in one or more directions. In all instances it will be observed,however, that it is the relative movement between the tool and workpiece that causes the work piece to be formed to a desired shape. As onespecific embodiment of my invention, 1 have chosen to illustrate anddescribe the invention incorporated in a lathe wherein the work piece,except for rotation about its center, remains stationary and the tool ismoved transversely and longitudinally thereof. As another specificembodiment of my invention I have illustrated its application to amilling machine wherein the tool, except for rotation about its center,remains stationary and the work piece is moved in two directions inorder that the tool may cut the work piece to a desired shape. It willthus be evident that my invention is applicable to a wide .variety ofmachine tools, and that when I speak of relative movement between thetool and work piece I include either an arrangement where the tool isstationary and the work piece moved, or the work piece is stationary andthe tool is moved, or a combination of the two.

Throughout the specification and claimsto follow I indicate that thework piece is formed to correspond tothe profile or shape of a master.By such language I do not intend to imply that the work piece is broughtto the exact shape of the master, but as will be evident to thosefamiliar with the art, the master will be formed so that the ultimateshape of the work piece produced is that desired, and that therefore theshape of the work piece may differ from that of the master by the amountof angularity, etc., in the mechanism. Furthermore, I use the termscontour, profile, shape, and the like, in a broad sense and not with anylimiting distinction between the profile of a two dimensional silhouetteor the surface configuration of a body, for example. In general, thepattern or cam dictates the desired shape of the work piece. 'I useprofile and contour interchangeably. The pattern has ass 7,824

3 the desired shape, although not necessarily the exact shape.

By strict definition one might be led to believe that profile is onlythe edge shape of a two-dimensional silhouette for example. Usually, itis spoken of as the edgeshape of a thin plate template, although such atemplate is a three-dimensional object. Usually ,contour is the surfaceconfiguration, or at least of a portion of the surface of athree-dimensional object. I intend to make it clear that inspeaking ofprofile or contour I mean the forming of a work piece to a shape asdictated by that of a template or pattern and work piece, it is notnecessarily identical in cona tour, and therefore the term correspondimplies that the pattern or template is purposely designed to result inthe desired contour of the work piece to be produced. This applicationis a parent application of my two divisional applications entitledSaturable Reactor Phase Shifter application Serial No. 145,992 filedFebruary 24, 1950, and "Dual Bridge Motor Control Circuit applicationSerial No. 145,991 filed February 24, 1950.

Referring to Fig. 1, I show my invention applied to an engine lathe Ihaving a head stock 2 adapted to be rotated at desired speed by anysuitable means 6| and having a tail stock 3. A carriage l is movablelongitudinally along the bed of the lathe on suitable ways 5 andsupports the tail stock 3. Also movable longitudinally along the bed ofthe lathe on suitable ways 6 is a carriage 'l. Mounted on the carriage'I is a cross-slide 8 movable on ways transversely of the bed of thelathe. The cross-slide 8 is provided with an adjustable tool support 9in which is secured a tool II]. An electric motor I l drives, throughthe necessary gear reduction I2, a worm or screw I3 for positioningthecross-slide 8 and tool I8 transversely of the bed of the lathe.Longitudinal movements of the tool I8, that is, movements of the toolparallel' to the center line of the lathe, are produced by means of amotor I4 operating a lead screw I6 through the intermediary of a gearreduction I5. Supported by the head stock 2 and tail stock 3 is a workpiece II, which for illustrative pur-' posesiis shown as being formed toa parabolic shape by the tool ID. The particular shape has nosignificance, it being apparent as the description proceeds that by myinvention a work piece may be formed automatically to any desiredcontour or shape. A master template or cam I8 is rigidly held inparallelism to the work piece I! upon. any convenient extension I8 ofthe lathe bed. The profile of the master I8 is the contour a v as havinga body member or envelope 2| which is firmly mounted to the cross-slide8 and a tracer arm 22 carried by a flexible diaphragm 23 forming a partof the enclosure 2 I The tracer assembly 20 constitutes an electrondischarge device, preferably a 2-element tube having a movable anode 24and a heated cathode 25. The envelope 2|, of which the diaphragm 23forms a part, may be of metal or of glass, but preferably of metal forstrength. It is preferably of such shape and construction that thediaphragm 23 will flex to allow movement of the anode 24 within theenvelope 2I as a result of positioning the tracer 22 through meansexternal to the envelope, such as engagement of the tracer 22 with theedge of the master template I8.

Such an electron discharge device or tube is preferably a high vacuumtube of the regulating type wherein the effective electron emitting orelectron receivin areas of the electrodes are varied without necessarilychanging the distance between the electrodes, as shown and described inthe patent to McArthur 2,142,857. I have shown the tube in quitediagrammatic fashion as being sufflcient for the present disclosure.Movement of the anode 24 relative to the cathode 25 causes a change inmagnitude of the electric current which flows through the device, andwhile the tube is not of the start-stop grid control type, neverthelessmovement of the anode away from the cathode in sufiicient extent mayreducethe current passage to zero.

In Fig. 2 I have not only shown the tracer assembly 20 to largerdiagrammatic scale, but have shown the complete electrical circuit forcontrolling the motor II by the tracer arm 22 in such manner that themotor I I will position the cross-slide 8 and consequently the tool IIItrans versely of the lathe, or in other words toward or away from thework piece I! as the tool III is traveled longitudinally. The action issuch that if the contacted edge of the master template I8 is a straightline parallel to the axis of the work piece I1, then the work piece I!would be turned to cylindrical form. Ifthe contacted edge of the masterI8 is a straight line, but inclined relative to the axis of the workpiece N, then the work piece I'l will be shaped to a taper. Theparticular showing of Fig. 1 is in general a parabolic curve on thecontacted edge of the master I8, and thus the form to be produced on thework piece I1.

Referring now in particular to Fig. 2, I will describe the electricalcontrol circuit whereby the direction and speed of rotation of the motorII is controlled by the inter-action of tracer arm 22 with the templateI8. In general the arrangement of Fig. 2 provides a phase sensitivebridge or network 28 controlling the motor II through the agency ofelectron discharge devices A and B. The description is premised on idealelectrical circuit conditions, and for simplicity the mote." controlcircuit will be described under conditions of full speed rotation of themotor in either direction, or under a balanced condition of no rotation.It will be apparent to those skilled in the art, as the descriptionproceeds, how variable speed of rotation of the motor in eitherdirection is accomplished between the limits of maximum speed ofrotation and zero speed.

In Fig. 3 I have plotted voltage values through the tubes A and B forzero rotation and for full speed motor rotation in either direction. InFig. 4 I have similarly plotted voltages across the armature of themotor II under the same operating conditions. Description will now behad with reference to Figs. 2, 3 and 4.

The phase sensitive bridge 23 is an alternating current bridge having asource of alternating current supply whose voltage is designated as E.The bridge comprises opposite resistance legs 21, 23 simultaneously handadjusted as illustrated. The remaining two legs and 3| of the bridge arereactive legs whose reactance is equal to each other and to theresistance of the legs 21, 28. With such a bridge the output voltage enis 90 degrees out or phase with the bridge A.-C. supply E.

The two reactive legs 30, 3| form alternating current windings of asaturable core reactor 29 having a direct current saturating winding 32,shunted by a capacitor 33, and joining a'direct current power sourcethrough the electron device 20. Thus positioning of the anode 24relative to the cathode 25 (of the device 23), through the inter-actionof tracer 22 with template I3, varies the direct current applied to thesaturating winding 32, and thus varies the reactance'or impedance toalternating current flow through the bridge legs 30, 3|.

The network is normally biased so that some D.-C. is flowing through thewinding 32, but not enough to result in motor rotation. Such a "neutralcondition exists when the tracer arm 22 is slightly biased in aclockwise direction (Fig. 2) by pressure against the template It. Fromsuch position a rise or recession of the shape of the templateencountered will cause a deflection. of arm 22 further clockwise or in acounterclockwise direction respectively. This will result in a variationin the amount of direct current flowing through the saturating winding32, and will result in shifting of the phase of the bridge outputvoltage eg in one direction or the other relative to the phase of thebridge supply voltage E, and in degree dependent upon the amount ofdirect current flow (relative to the neutral value) through thesaturating winding 32 and correspondingly upon the direction and amountof deflection of the arm 22.

Control tubes A and B are connected back to back with their grids inphase, but the plates 180 degrees out of phase. The grid voltages e anden are (as shown) equal and in phase; the grid transformer 34 serving toseparate and insulate the grid circuits of the tubes A and B.

At balance, i. c. with the motor stationary, the grid voltage e; is 90degrees out oi, phase with tubes A and B. For example, it is plus 90degrees with reference to A and minus 90 degrees with reference to B.This is shown in the bal anced" graph of Fig. 3. Voltage conditionsthrough the armature 35 of motor II are shown in the balanced graph ofFig. 4, wherein actually the armature receives equal alternate voltagesof opposite polarity to 'efiectively plug it against rotation. Thecurves of Figs. 3 and 4 are plotted on theoretical ideal values forexplanatory purposes only. Actually the armature voltage will bedistorted by inductance.

The value of en, and consequently of 81, remains substantially constantunder the assumed ideal condition of maximum tube conductance.

current of one sign. The condition for full speed 6 reverse directionrotation is shown in the lower graphs of Figs. 3 and 4.

The electron discharge devices A and B are indicated as having plateanodes 36 and 31, control grids and 4|, and heated filament cathode 33and 33 respectively. The cathode 38 of tube A is connected to the anode31 of tube B, while the anode 36 of tube A is connected to the cathode33 of tube B.

Inasmuch as I supply both the grid and the plate of each tube with analternating current, the phase relation between the grid and platevoltage determines the point in the wave at which current begins to passin each cycle; hence the average amount of current passing through thevalve. Current can pass through avalve in only one direction, andinasmuch as the two valves A and B are opposedly connected in parallelin the alternating current circuit shown, each valve will pass one-halfof the alternating current wave. I

, may vary the amount of current passing through each valve by causing ashifting of the phase of the grid voltage relative to the plate voltage,which is accomplished as previously mentioned by the phase shiftingbridge or network 26.

As mentioned, the grids of the two tubes A and B are in phase, but theplates are out of phase by 180 degrees. Voltages 331 and eg2 are alwaysequal, so that the tubes are both conducting during one-half cycle inthe neutral condition. During one-half cycle the grid is in phase withthe plate of each tube, and therefore an alternating current platecurrent is flowing through the motor. This current flow through thetubes A and B is illustrated by the shaded sectioning on the Balancedgraph of Fig. 3, and on the "Balanced graph of Fig. 4 is illustrated bythe shaded portions the voltages across the armature 35. In Fig. 3 bothshaded sections are above the line as current flows through the tubes inthe same direction. However, the voltage through the armature 35 ispositive from one tube and negative from the other as illustrated inFig. 4, and thus in the neutral or balanced condition the motor isplugged because alternate half cycles are in opposite direction.

With reference to the bridge, under one condition of unbalance there ian increase in direct current flow and under the other condition ofunbalance there is a decrease of direct current flow, and this causes anunbalance of the circuit in one direction or the other, or a shifting ofphase in the output bridge voltage en relative to the supply voltage E.Unbalance, for example an increase, in direct current flowing throughthe saturating winding 32, reduces the impedance of bridge legs 30 and3|. They become unbalanced relative to legs 21 and 23, which makes thereactance less than the resistance. This shift in phase of so is aboveor below degrees out of relation with E. As the grid voltage swings foran increase or decrease, toward the right or toward the left, it tendsto brin it nearer in phase with tube A (or B) or nearer degrees out ofphase with B (or A). If A is fully conducting (and B is oil) the motorrun in one direction on pulsating D.-C. smoothed out by the choke 42.

In Fig. 2 I have illustrated a feed back circuit including a resistance43, a capacitor 44, and a reactance 45, connected in series across thearmature 35. Further, in the series group is a portion of a resistor 41as determined by the position of a contact arm 46 manually adjustable.The effective direct current voltage across the armature 35 is a measureof its speed of rotation, and therefore the rate of change of voltage isa measure of rate of change in speed. This gives a voltage in the feedback circuit only when speed is chan ing and opposing the input duringchange in speed. That is, it adds goin up and subtracts going down. Theresult is that with the feed back voltage adding, upon an accelerationthe motor speeds up or tends to overcome its inertia, and in coming downit bucks and tends to slow it down faster so that the motor does notovertravel. This effect has been plotted in Fig. 5.

From the preceding description it will be apparent that the speed anddirection of rotation of the motor is under the control of the tracerassembly 20 and specifically of the interrelation between the tracer arm22 and the template l8.

Referring again to Fig. I, assume that the motor I4 is being operated ata uniform speed of rotation in direction such that the cross-slide 8 andtool I are being traveled at a uniform speed from right to left alongthe work piece I], and at the same time the tracer assembly 20 is beingtrav eled from right to left along the template IS. The adjustment issuch that the tracer arm 22 is slightly pressed against the edge of thetemplate l8. Under this bias condition the motor II is plugged and notransverse movement of the tool In or of the tracer assembly 20 is had.This is the condition that would exist if the contacted edge of thetemplate I8 is a straight line parallel to the axis of the work piece l1and would result in the turning of the work piece I! to a cylindricalform.

If, as the tracer assembly 20 continues to move toward the left, itencounters a change in shape of the template I8 whereby (referring toFig. 2) the tracer arm 22 is deflected in either a clockwise orcounterclockwise direction relative to the envelope 2|, then the directcurrent passage through the device 20, and consequently through thesaturating winding 32, will be either increased or decreased (dependingupon the direction of deflection) with consequent rotation of the motorarmature 35 in proper direction to position both the tool l and tracerhousing 2| transversely relative to the work piece I1. This provides afollow-up on the tracer assembly whereby the envelope 2| is positionedin the same direction to the movement of the tracer arm 22 to follow upand tend to return the current flow through saturating winding 32 to theneutral value.

For example, if (referring to Fig. 1) the edge of thetemplate I8 isincreasing in distance from the center line of the work N, then thetracer arm 22 will be continually moved relative to the envelope 2| indirection to cause the motor to keep backing the tool l8 away from thecenter line of the work l1, and thus produce an increasin diameter ofthe work piece I! as the tool moves toward the left. As previouslymentioned, the motor II is controlled not only as to direction ofrotation, but also as to speed of rotation, dependent upon the magnitudeof departure of the contacted edge of template l8 from a straight lineparallel to the axis of work piece ll.

In describing the operation of the motor for transverse movement of thetool It! and tracer assembly 28 I have so far assumed that the motor l4runs in one direction at a uniform speed, thus traveling the carriage Ilongitudinally of the work piece at a uniform speed from right to left.Preferably the tracer assembly 28 also controls speed of rotation of themotor l4 and thereby the speed of longitudinal travel of the tool alongthe work piece. The need for such control is known to those skilled inthe art. If the contacted edge of the template I8 approaches or recedesfrom the center line of the work piece II (as demanding a taper) thelongitudinal speed of travel of the tool |8 should be reduced inproportion to the steepness of the desired taper. For example, as anextreme, if the tracer arm 22 reaches a shoulderon the edge of thetemplate l8, normal to the axis ofthe work piece, it is necessary tocompletely stop longitudinal travel of the tool III while the tool movestoward or away from the center of the work piece in transverse directionfor finishing such a shoulder. Thus in general as the tool (under theguidance of the tracer) moves in either direction transversely of thework piece the longitudinal speed of travel of the tool is reduced froma maximum. When turning the work piece to cylindrical form, i. e. withno movement of the tool transversely of the work piece, thenlongitudinal speed of travel of the tool is at maximum.

This 1 term a neutral" condition.

The reactors additionally each have two direct current windings, onecarrying the D.-C. input from conductors 48, 49 (Fig. 2), and the otherbeing a direct current bias winding. In the drawing arrows indicate thefact that the direct is not ufging thetool transversely of the work.

piece, and desirably the motor I4 is rotating at its maximum speed. tral.value of D.-C. input to the conductors 48, 48 I desire full speedrotation of the motor l4. For either an increase or decrease of D.-C.input through the conductors 48, 49 I desirably decrease the speed ofthe motor l4 toward zero. These conditions I have graphically plotted inFig. '7.

In the circuit of Fig. 6 the bridge 58 is current sensitive, butdeparture of balance in either direction increases the direct currentvoltage e0 output of a rectifier 54. "Upon, the D.-C. output 6c Isuperimpose an alternating current from a transformer 55 degrees out ofphase. voltage 6; is therefore equal to es plus the superimposed out ofphase alternating current voltage and Cg is applied to the Thyratron 56for control thereof. The plate voltage Ep across the tube 56 passesthrough the armature of the motor H for speed control thereof. Referringto Fig. 7, the shaded portion of the graph indicates the band ofconductance of the tube 56, from which it will be seen that as eaincreases the conductance of the tube 56 decreases until it fails toturn on at all and the motor M has zero speed.

From the above it will be apparent that as the D.-C. input-to theconductors 48, 49 varies in either direction from the neutral value, theconductance of the tube 56 decreases and the speed of the motor 4decreases from a neutral maximum speed. While I have shown the controlcircuit for the motor I in Na 2. and thatior the In other words, underneu- 9 motor H in Fig. 6, it is to be understood that the two circuitsmight have been shown in a single figure of the drawing.

In Fig. 8 I do show schematically the control of a motor l M reversibleat variablespeed and a motor I4A operating in one direction at variablespeed, both simultaneously from the D.-C. input through conductors 48,49. The motors MA and A are alternating current type motors, and aparticular feature of my invention is that the control of speed isentirely by phase shift or amount of lead or lag in phase relative tothe line, and wherein the voltage tends to remain constant. Thus themotor speed control in accordance with my invention is by phase shiftrather than by magnitude of voltage or current. The alternating currentvoltages E1 and E3 have voltage values remaining substantiallyproportional to line voltage. The phase, however, of E1 and of E3 isshifted by the bridges X and Y respectively simultaneously and in thesame direction and amount.

Referring to Fig. 9, wherein I plot phase conditions of the voltages inconnection with motors HA and A, it will be noted that the solid curvesrepresent phas conditions under neutral condition of D.-C. input throughthe-conductors 48, 49,

whereas the dotted lines show voltage phase con-' ditions at the extremeof phase shift either way from the neutral. It is a characteristic ofthe circuit that the phase shift will not be over 90 degrees either wayfrom neutral. It will be observed that the motor I IA has a winding 51connected across E1 and at 90 electrical degrees thereto a winding 58conn cted in series with a capacitor 59 and across E2. The motor A hassimilar windings 51A, 58A 90 electrical degrees apart. but does not havethe capacitor 59.

Referring to the uppermost graph of Fig. 9 which is representative ofconditions appurtenant to motor HA, it will be observed that under theneutral condition of D.-C. input to the conductors 48, 49 E1 and E2 arein phase with each other for zero motor speed and are 90 degrees out ofphase with the line voltage due to the efiect of capacitor 59 on voltageE2. Voltage F1 can be shifted by bridge X to be in phase with the lineor 180 out of phase with the line, i. e. it leads or lags E2 by 90degrees as an extreme. Intermediate phase relation between Erand Ezdetermines not only the direction but also the speed of rotation of themotor A.

Under neutral conditions E4 is in phase with the line and E3 is 90degrees out of phase with both the line and E4. This means that underneutral condition the motor HA is rotating at its maximum speed.Shifting of the phase of E: 90 degrees either way from the neutralcondition means that for one direction of phase shift E3 will approachin-phase relation to E4 and the motor armature will approach zero speed.Under the other extreme of phase shift Ea will approach 180 degreesout-of-phase with E4 and the motor armature will approach zero speed ofrotation. Thus from a neutral condition wherein motor MA is rotating atmaximum speed the speed will be decreased upon any shift in phase of E3in either direction relative to E4, and the speed variation betweenmaximum and zero will depend upon the degree of phase shift.

The bridgrs X and Y of Fig. 8 areof the type designated 25 in Fig. 2without. however, in this case haying tle feedbacks at 46, 41.

Up to the present I have been describing what I term a 2-element controlof a lathe, namely,

control of transverse motion of the tool and of longitudinal movement ofthe tool. For certain operations it may be desirable to provide a 3-element control of the lathe, namely, to include with the control oftransverse and longitudinal movement of the tool a control of speed ofrotation of the work piece relative to the tool. This so that cuttingspeed of the tool may be held constant, i. e. the speed of rotation ofthe work when cutting at one diameter to be proportionally greater orlesser than the speed of rotation when cutting at a different diameter.To accomrlish such control I provide for rotating the work piece I!through the necessary gears 60 by means of a motor 6| similar to themotor HA and controiled in similar manner insofar as unitary directionalrotation words, the motor 6| would rotate normally in a singledirection, but its speed of rotation would depend upon the transverseposition of the tool [0, and consequently upon the diameter of the workpiece to which the tool were cutting.

For dictating to the control circuit of motor GI the transverse positionof the tool I0 I provide a cam 62 (Fig. 1) fastened to and carried bythe cross-slide 8 in its transverse positioning relative to the workpiece l1. Fixed to the carriage l is a tracer assembly 63 having itscontact arm engaging the profile of the cam 62. Thus as the cross-slide8 is positioned toward or away from the axis of the work piece I! thecam surface 62 would engage in greater or lesser extent the tracer 63for control of speed of rotation of the motor 6| rotating the work pieceI1. The electrical control of the motor 6| through the agency of thetracer 63 is similar to that described in connection with Fig. 6, sothat it does not appear necessary to duplicate the drawing anddescription.

My invention is equally applicable to other types of machine tools ormaterial working machines, and in that connection I will now describe myinvention as applied to a vertical milling machine. In Fig. 10 I show aview looking down on a vertical milling machine having a column 64, awork table 65, and a rotatable form milling cutter 66. The work table 65is movable along ways 61 on a saddle 68 through the agency of a motor69, gear reduction 10 and screw H. The saddle 68 is positionable alonghorizontal guideways 12 of a knee (3 which is supported in verticalguideways 14 formed on the column 54. The cutter '66 while rotating isnormally in fixed axial position. On the work table 65 is a rotatablework holder 15.

At 16 is shown a typical work piece consisting of a concave forging ofmore or less elliptical shape and in rough form having a raised blankface extending around its entire periphery. The machining operationwhich I have chosen as illustrating my invention includes forming a maleflange face onthis blank face. The cutter 66 is suitably shaped torelieve the outer edge of the flange and by my invention the work pieceis automatically moved along the guideways 61, while the work 16 isbeing rotated, so that the cutter accurately forms the outer profile ofthe raised portion of the flange.

The work piece 16 is shown as being secured to the work holder 15 bycommon clamping means. The machining of the work piece 16 is completedin one revolution of the work holder 15 during the revolution of thework piece, it being moved relative to the cutter 66 along the guideways61. The work holder 15 has a horizontally extending skirt 11 forming acam or template, the contour is concerned. In other of which is formedto produce the desired con-' tour of the raised portion of the flange onthe work piece 15. A raised barrier 18 is preferably employed to holdchips cut from the work piece from scattering.

Supported by the saddle 68 is a tracer assembly 18 having a tracer arm88 engaging the periphery of the cam 11. The device 19, 88 controls themotor 68 which drives through the gear 18 and lead screw 1| forhorizontally positioning the work table 65 along the ways 61. Throughengagement of the tracer arm 88 with the periphery of the cam 11 themotor 68 is energized to position the work piece 16 and cam 'I'Itransversely in either direction relative to the axially stationarymilling cutter 86.

In Fig. 11 I show an elevation of a portion of the milling machine ofFig. 10. I provide a second cam or template 8| rotatable with the workholder 15, the work I8, and the cam 11. Engaging the cam 8| is thecontact arm 83 of a tracer 82 mounted on the nonrotatable table 65. Thetracer 82, 83 is, however, movable along the ways 61 of the saddle 68with the rotatable and the nonrotatable portions of the work table 65. Amotor (not shown) for rotating the rotatable portion of the work table65 is movable along the ways 61 with the entire work table assembly.Such motor is controlled by the tracer 82, 83 in engagement with the cam8I and functions to provide a speed of rotation of the work piece 16depending upon the cam profile 8 I.

In general the arrangement is such that the cam 11 provides thetransverse movement of the work 16 relative to the cutter 66, and whilethe work I6 is making one complete revolution. The

cam 8| functions to determine the speed of rotation of the work 18relative to the cutter 66 during the single revolution of the workpiece. The motors under the control of the tracer 19, 88 and the tracer82, 83 are of the type described and controlled similar to motors I Iand I4 respectively of Fig. 1. The tracer I9 may be similar to thetracer 28, of Figure 2, and control a bridge similar to the bridge 26.This bridge in turn may control oppositely connected tubes similar totubes A and B of Figure 2. The output of these tubes will control themotor 69, both as to direction and speed of rotation. Such control ofthe motor 68 will, of course, reciprocably position the worktable 65 todetermine the shape of the workpiece I6. The tracer 82 may be similar tothe tracer 28 and control a circuit similar to the circuit of Figure 6.Thus the motor controlled by tracer 82 will be variable in speed in asingle direction, and hence the speed of rotation of the workpiece I6may be varied in accordance with the template 8| to take into accountthe slower speed desired during movement of the worktable 65.

In Figs. 12, 13 and 14 I illustrate a further embodiment of my inventionwherein the lathe cutting tool I8 is positioned transversely relative tothe work I I through the agency of a hydraulic motor comprising acylinder 86 and piston 81, the latter positioning the cross-slide 8through the agency of a piston rod 88. The tool I8 is positionedlongitudinally along the work I! through the agency of a cylinder 89,piston 88 and piston rod 9|. For rotating the work piece I! I provide ahydraulic or fluid pressure motor 82.

In Fig. 13 I illustrate that the control of the tool is a combination ofelectrical and hydraulic operation. The tracer assembly 28 (as in Fig.2)

12 controls a current sensitive bridge 28, which In turn selectivelycontrols theoutput of the tubes A and B to the conductors 84, 88.Connected in series in the conductor 84 are solenoid windings 88, 84. I

For control of the hydraulic motor 88 I provide an oil pilot valve 86,whose movable element is positioned by and with the solenoid core 88against the bias of a spring 81 and under the influence or the solenoidwinding 88. For positioning of the hydraulic motor 88 I provide avariable fluid resistance 88 whose movable ele-.

ment is positioned by and with a solenoid core 88 against the bias of aspring I88 and under the influence oi. the solenoid winding 84. Thepilot valve and the adjustable fluid resistance 88 may be 01 the typedisclosed and claimed in the patent of Clarence Johnson, number2,872,426, issued March 27, 1945.

I show an oil pump I8I- driven by a motor I82 and drawing its supply ofoil from a sump I88. Oil under pressure is supplied the pilot valve 88by the pump |8| through a pipe I84 From the pilot valve 86 oil issupplied to one end or the other 01' the hydraulic motor 86 through thepipe I85 or I86. Drainage from the pilot 88 is returned to the sump I88through a pipe III.

In connection with the hydraulic motor 88 and adjustable resistance 98 Iprovide switching valves I88, I88 arranged to be moved together toeither a normal or a rapid traverse" position of operation for thehydraulic motor 88. The valves I88, I89 are shown in Fig. 18 in the"normal operating position. 011 under pressure from the pump I8I isforced through the pipe II8, the valve I88 and the pipe III to one endof the cylinder 89. Oil from the other end of the cylinder 89 passesthrough a pipe II2, the valve I88, the valve I89, a pipe I I3, theadjustable resistance 86 and a pipe II4 to the sump. The regulation ofthe variable resistance 98 for anydisplacement of the core 98 fromneutraldetermines the rate of flow of oil through the pipe H2 and consequently the rate of travel of the piston rod 8I toward the left in thedrawing of Fig. 13. Thus the rate of longitudinal travel of the tool I8along the work piece I! 'is controlled by the variable resistance of 88to passage of oil therethrough from the left-hand end of the cylinder89.

In Fig. 14 I show the passage relation of the switching valves I88, I89for a rapid return" of the piston rod 9| frpm left toright in Fig. 14. I

That is, for a rapid return of the tool I8 to the begirming of itsworking travel. In such position of the valves I88, I89 oil from thepump, I8I passes directly through the pipe I I8, the valve I88 I and thepipe IIZ; while oil from the right-hand -end of the cylinder 88 passesdirectly through the pipe III, the valve I88, the valve I88, the pipe II4 to'the sump. Thus on the rapid return of the piston rod 9| there isno throttling of its speed of travel by the variable resistance 98, andthus the tool is traversed to the right at maximum I energization of thesolenoid windings 98, 84.-

Adjustment of the springs 81, I88 in relation to this predeterminedenergization results in a position of the moving parts of the relay 85,and of the fluid resistance 98, such that a "neutral or normal conditionpersists. Under this condition 13 I the pilot 85 is locked against thepipes I05, I08 so that there is no motion of the piston rod 88. At thesame time the movable part of the fluid resistance 98 is in its positionof allowing the greatest leakage oi oil from the cylinder 89, and thusmaximum speed of travel of the piston rod SI. This is a condition whichwould exist if the tool I is cutting a cylindrical form on the workpiece I1. Upon change in shape of the template I8, the energization ofthe windings 83, 84 is correspondingly changed in amount and directionto vary the direction of travel of the piston rod 88 and the speed oftravel of both piston rods 88 and SI.

In Fig. 15 I illustrate a measuring circuit employing the phasesensitive network 28 of Fig. 2 controlling a direct current type motor II through the agency of control tubes A and B. The network 26 receivesdirect current input through the conductors 48A and 48A from abalanceable network II5.

Whereas, in Fig. 2, I have illustrated the variable area electrondischarge device 20 as having its anode 24 positionable by the tracerarm 22- and the envelope 2| being moved with the crossslide 8 forfollow-up; I herein indicate that the envelope I I6 of the electrondischarge device III is fixed and that the follow-up or balancing of thenetwork H is accomplished through the movement of a contact arm I I8over a resistance H9. The envelope IIS contains a stationary cathodeI20, a stationary anode I22, and a movable anode I2I; the latterpositioned through the agency of a Bourdon tube I23, which may besubjected to a pressure or temperature condition. The Bourdon tube I23is representative only of any measuring device sensitive to the value ofsome variable, such as temperature, pressure, flow, position, movement,or the like, and whose magnitude or change in magnitude is desirably tobe continuously indicated as by the index I24 relative to the scale I25.It is, of course, possible to have the anode I2I moved by a tracer arm(such as 22). The particular feature of the circuit in Fig. 15 is in thecontrol of the motor II with an electrical balance of the system, ratherthan by mechanically positioning the envelope H8; in comparison to thesystem described in connection with Fig. 2.

Furthermore, the network II5 of Fig. 15 provides a reference arrangementcompensating for any variations in emission of the device I I1,variations in the electrical characteristics of the direct currentsource, etc. The direct current source is connected directly to thestationary cathode I20 and the emission across I2DI22 provides thereference compensating the network II5 just mentioned relative to theemission across I28-I2I, which is controllable by movement of theBourdon spring I23.

In operation, when pressure within the Bourdon tube I23 changes, thenthe position of I2I relative to I20 is varied, thus varying theelectrical values within the loop including the members I20, I2I, I28and the D.-C. source. This loop becomes unbalanced in relation to theprevious balance with the loop comprising I20, I22, H9 and the source.The direction and extent of unbalance is efiect-ive through theconductors 48A, 49A to control the phase sensitive bridge 26, andthereby control the direction and speed of rotation of the motor II. Themotor II is connected to position the contact arm II8 over theresistance IIB for again balancing the network H5, and at the same timethe motor positions the pointer I24 relative to the scale I25 to provide an indication of the pressure or other variable to which the deviceI23 is sensitive.

In Fig. 16 I show a network I21 for energizing the conductors 48A, 49A(Fig. without providing the reference compensating portion of thecircuit, Fig. 15. The electron'device 28 has a single cathode 25 and ananode 24.

In Fig. 17 I show a circuit for the control of a motor II from a D.-C.input over conductors 48,

48 and employing two phase sensitive bridges I28.

I28 for control of the electron devices I30, I3I, which may beThyratrons to control larger direct current motors than-those shown inFig. 2

The bridges I28, I29 are similar to each other and in general aresimilar to the bridge 28 of Fig. 2. Each bridge has a saturable corereactor, but in bridges I28 and I28 there is a direct current biasapplied to a winding of each reactor in addition to the direct currentcontrol winding. In bridge I28 the bia is opposin the control windingwhereas in bridge I28 it is additive. Inasmuch as the bias is equal inthe two bridges, the current across conductors 48, 48 is zero at abalanced condition with the motor II not rotating. Under this conditionthe reactors are equally saturated by the common bias current. Unbalanceof the supply to 48, 48 in one direction produces increased saturationof bridge I28 and decreased saturation of bridge I29. This produces agrid voltage on tube I30 more nearly in phase with its plate and less inphase on the plate of tube I3I. Reversal of the direct current supply to48, 48 produces an opposite effect.

While I have chosen to illustrate and describe certain preferredembodiments of my invention, it will be understood that my invention isapplicable to many other problems and that I am not to be limited to theembodiments described.

What I claim a new, and desire to secure by Letters Patent of the UnitedStates, is:

1. A measuring system for indicating a variable such as a position orvalue including in combination, a balanceable direct current circuit,means positioned representative of the variable for disturbing thebalance of the circuit, a phase shifting network controlled by thedirect current output of said circuit, said network including oppositereactance arms on a saturable core reactor structure, electron dischargemeans selectively controlled by phase values of network output voltage,a, motor connected to said discharge means and whose direction and speedof rotation is controlled by the electron discharge means, and balancingmeans in said circuit positioned by the motor as a measure of thevariable.

2. The system of claim 1 including reference circuit means compensatingfor disturbing electrical characteristics of the direct currentbalanceable circuit.

3. A motor control circuit including two phase shifting alternatingcurrent bridges each including 9, saturable core reactor, said bridgeseach having opposite reactance arms on said reactor, a substantiallyconstant direct current bias for each 01' said reactors, a variablesource of direct current as a control to each of said reactors, thevariable control direct current additive with the bias on one reactorand opposing on the other, electron discharge means selectivelycontrolled by the phase of the output voltages from the bridges, and amotor connected to said discharge means and controlled as to directionand speed of rotation by the electron discharge devices.

4. In anelectrical system for maintaining a given energization conditionof a power utilizing device, a unidirectional variable current passingdevice to cause variable energization of said power utilizing device, a,controllable phase shift bridge having an output voltage for controllingthe current passed to said power utilizing device by said unidirectionalvariable current passing device, means for energizing said bridge froman A. C. source, two opposite reactance arms in said bridge, a saturablecore for said reactance arms, control winding means for effectingvarying degrees of saturation of said saturable core to shift the phaseof the bridge output voltage relative to said A. C. source and hence theenergization of said power utilizing device, excitation means forexcitin said control winding means ata first condtion of excitationcorre-- sponding to the given energization condition of said powerutilizing device, unbalancing means for changing the excitation on saidcontrol winding means to shift the phase of said bridge output voltagefor varying the energization condition of said power utilizing device,and mechanical linkage means connectedbetween said device and saidunbalancing means and responsive to the change of energization of saidpower utilizing device for at least retardin the effect of saidunbalancing means.

5. In an electrical system for tending to maintain a constant velocityof rotation of a motor, a thermionic tube to cause variable energizationof said motor, a phase shift network connected to said tube and havingan output voltage for controlling the current passed to said motor bysaid tube, means for energizing said network from an A. C. ource, twoopposite reactance arms in said network, a saturable core for said arms,control winding means for effecting varying degrees of saturation ofsaid saturable core to shift the phase of the network output voltagerelative to said A. C. source and hence vary the rotational'speed ofsaid motor, excitation means for exciting said control winding means ata given condition of excitation corresponding to said constant velocityof rotation of saidmotor, unbalancing means for changing the excitationon said control winding means to shift the phase of said network outputvoltage for varying the rotational velocity of said motor, andmechanical linkage means connected between said motor and saidunbalancing means and responsive to the movement of said motor for atleast retarding the efiect of said unbalancing means.

6. A motor control circuit including in combination an alternatingcurrent network com prising a bridge having opposite resistance-arms andopposite reactance arms, the reactance arms included in a saturable corereactor structure,-

' a direct current control windin for the reactor for varying theimpedance of the reactance arms, a source of alternating current voltagefor the network, an alternating current output circuit from the networkto deliver a substantially constant network output voltage shiftable inphase relative to the phase of, the said source by variation in theamount of direct current' supplied to said control winding, a pair ofopposedly connected discharge devices selectively controlled by thephase of the network output voltage, and a motor connected to saiddevices and whose rotation is controlled by the output voltages of thepair of discharge devices. I

7. A motor control circuit including in combination an alternatingcurrent network com- 16 prising a bridge having opposite resistance armsand opposite reactance arms,'the reactance arms included in a saturablecore reactor structure,

" a direct current control winding for the reactor for varying theimpedance of the reactance arms, a source of alternating current voltagefor the network, an alternating current output circuit from the networkto deliver a substantially constant network output voltage shiftable inphase relative to the phase of the said source by variation in theamount of direct current supplied to said control winding, a pair ofopposedly connected discharge devices selectively controlled by thephase of the network output voltage, a motor connected tosaid devicesand whose rotation is controlled by the output voltages of the pair ofdischarge devices, and means controlled by the rotation of said motorfor varying the degree of energization of said direct current winding.

8. In an electrical system for establishing a given balancedenergization condition of a power utilizin device, a controllable phaseshift bridge having an output voltage for controllin the current passedto said power utilizing device, means for energizing said bridge from analternating current source, two opposite reactance arms in said bridge,a saturable core for said reactance arms, control winding means foreffectin varying degrees of saturation of said saturable core to shiftthe phase of the bridge output voltage relative to said alternatingcurrent source and hence the energization-of said power utilizingdevice, excitation means for exciting said control winding mean at abalance condition of excitation corresponding to the balancedenergization condition of said power utilizing device, and unbalancingmeans for changing the excitation on said control winding means to shiftthe phase of said bridge output voltage for varyin the energizationcondition of said power utilizing device;

9. In an electrical system for maintaining a given balanced energizationcondition of a power utilizing device, a controllable phase shift bridgehaving an output voltage for controlling the current passed to saidpower utilizing device,

means for energizing said bridge from an alterchanging the excitation onsaid control winding means to shift the phase of said bridge outputvoltage for varying the energization condition of said power utilizingdevice, and mechanical linkage means responsive to thevchange ofenergization of said power utilizing device and connected to saidunbalancing means for at least retarding the eflect of said unbalancingmeans.

10. In an electrical system for tending to maintain a constant velocityof a motor, a phase shift network having an output voltage forcontrolling the current passed to said motor, means for energizing saidnetwork from an alternating current source, two opposite reactance armsin said network, a saturablebore for said arms,

control winding means for eflecting varying degrees of saturation ofsaid saturable core to shift the phase of the network output voltagerelative to said alternating current source and hence vary the speed ofsaid motor, excitation means for exciting said control winding means ata balance condition of excitation corresponding to said constantvelocity of said motor, unbalancing means for changing the excitation onsaid control winding means to shift the phase of said bridge outputvoltage for varying the veloc ity of said motor, and mechanical linkagemeans responsive to the change of velocity of said motor and connectedto said unbalancing means for varying said excitation means in adirection to at least retard the effect of said unbalancing means.

11. A motor control circuit including in combination, a phase shiftingnetwork having a substantially constant value output voltage ofadjustable phase relative to the phase of the alternatin current voltagesupply to the network, said network including two opposite reactancearms, a saturable core for said reactance arms, an adjustable directcurrent control for the network for efiecting varying degrees ofsaturation of said saturable core, a pair of opposedly connectedelectron discharge devices selectively controlled by the phase of thenetwork" output voltage, and a motor connected to said devices and whoserotation is controlled by the output voltage of the pair of electrondevices.

12. A motor control circuit including in combination, a phase shiftingnetwork bridge having a substantially constant value output voltage ofadjustable phase relative to the phase of the alternating currentvoltage supply to the network, said bridge including opposite reactancearms on a single saturable core structure, an adjustable direct currentcontrol for effecting varying degrees of saturation of said saturablecore structure, a pair of opposedly connected electron discharge devicesselectively controlled by the phase of the network output voltage, and amotor connected to said devices and whose direction and speed ofmovement is controlled by the output of the electron devices.

13. A motor control circuit including in combination, a phase shiftingnetwork having an output voltage of adjustable phase relative to thephase of the alternatin current voltage supply to the network, saidnetwork including two opposite reactance arms, a saturable core for saidreactance arms, direct current control means in said network toefiectvarying degrees of saturation of said saturable core for adjustingthe phase or its output voltage, electron discharge means selectivelycontrolled by the phase of the network output voltage, and a motorconnected to said electron discharge means and whose speed is controlledby said electron discharge means.

14. The circuit of claim 13 including means sensitive to a variable forvarying the direct current.

15. The circuit of claim 14 wherein the motor is a shunt wound directcurrent type having a direct current energized field and having anarmature receiving pulsating direct current from the electron dischargemeans.

16. The circuit of claim 14 includin a feedback circuit from the motorto the direct current control mean imposing thereon a feedback voltagerepresentative of rate of change in motor speed.

17. The circuit of claim 14 including an antihunt feedback circuit fromthe motor to the direct current control means imposing thereon afeedback voltage only when motor speed is changing.

18. A motor control circuit including in combination, a phase shiftinnetwork having a substantially constant value output voltage ofadjustable phase relative to the phase of the alternating currentvoltage supply to the network, said network including two oppositereactance arms, a saturable core for said reactance arms, direct currentcontrol means delivering direct current of changeable potential toeffect varying degrees of saturation of said saturable core foradjusting the phase of its output voltage, electron discharge meansselectively controlled by the phase of the network output voltage, and amotor connected to said electron discharge means and controlled by saidelectron discharge means.

ANTHONY J. HORNFECK.

REFERENCES CITED The following references are of record in the file ofthis patent:

